This story is a partnership between  Grist  and  Chicago Public Media ,  a public media company serving the Chicago metropolitan region. Renee Costanzo cranked on the rusty pulley with both hands, watching the greenhouse roof creak open in sections. A breeze of spring air swept over 12,000 seedlings lined up in plastic trays in the Kilbourn Park greenhouse. Costanzo, the Chicago Park District’s only full-time employee at the northside greenhouse, spearheads a months-long effort to grow more than 15,000 plants, including vegetables, greens, and flowers, to get them ready in time for the Kilbourn Park’s annual plant sale. The massively popular sale, which took place earlier this month, typically draws upwards of 1,100 people every year, with local gardeners lining up around the park waiting to snatch up plants at $4 a piece. But this year, attendance broke records — over 2,300 shoppers turned out.…